The initiative – called the Californians Against Sexual Exploitation Act [PDF] – would toughen penalties for sex trafficking and add those convicted of the crime to the state’s sex offender registry. Most significantly, it also would require all registered offenders to surrender their “Internet identifiers” to law enforcement, including user names and email accounts.

“Every girl sold on the street today is also being sold on the Internet,” said Daphne Phung, executive director of the advocacy group California Against Slavery.

Chris Kelly, the former Facebook executive, has contributed $1.6 million to the initiative since December, according to campaign finance filings. That amount is 94 percent of all donations.

The spending marks Kelly’s return to campaign politics after a failed bid for state attorney general in 2010. He finished third in the Democratic primary despite spending millions of dollars of his own money.

In that race, Facebook’s spotty history on user privacy and safety opened Kelly to questions about how he’d protect Californians as residents move more of their lives onto digital networks.

In 2007, the New York attorney general's office ran a sting against Facebook that tested how quickly the social media giant addressed complaints about sexual predators. Facebook administrators took 10 days to respond to complaints about an exchange in which a predator attempted to lure a 13-year-old girl into an intimate conversation. Investigators had written the messages and filed the complaints.

For Kelly, who joined Facebook in 2005, that investigation sped up movement to address a surge in cases in which people use the Internet to commit sex crimes. The Web is increasingly the busiest marketplace for prostitution and human trafficking.

Kelly said he worked with then-New York Attorney General Andrew Cuomo to pass the “e-STOP” legislation that implemented many of the monitoring measures Kelly is attempting to bring home to California. He helped write legislation last year, SB 57, which carried the sex offender provisions that are in the ballot measure. The bill faltered in the state Assembly.

The issue of Internet identifiers is controversial, as it intertwines concerns over online privacy with law enforcement’s access to the reams of data that people generate in the course of daily activities. The American Civil Liberties Union was among the bill’s opponents.

Kelly said he decided to make his case directly to voters, with the help of his personal fortune.

“I’ve managed to do very well in California,” Kelly said, “and I’m very willing to give that back to the state, hopefully in the form of a safer Internet.”

He partnered last fall with Phung, a longtime activist for strict laws against human trafficking, to broaden the effort.

In 2010, Phung had attempted to get an anti-human trafficking measure on the ballot, but was unable to fund the signature-gathering effort. “I can provide the grassroots and the volunteers,” she said. “What we were missing is the funding piece of it.”

Kelly has poured hundreds of thousands of dollars at a time into the measure’s coffers to secure it a place on the November ballot. The secretary of state’s office qualified the anti-trafficking initiative in May.

While Kelly already has invested heavily in the campaign, he said he intends to make future contributions if and when they become necessary. Right now, the initiative’s supporters are working to broaden their support and revenue sources.

People previously have been hesitant to donate large sums to little-known groups or causes, Phung said. Kelly’s involvement and cash have given the campaign more legitimacy.

But Phung said it’s still challenging to convince potential donors – and, in the coming months, voters – that sex traffickingis a crime that occurs regularly in the U.S. “They think it’s something that happens overseas, with children being forced into brothels,” Phung said.

Kelly said he’s focused on shattering that perception as well.

Funding a successful ballot measure also can help build credentials for those aspiring to elected office. Kelly acknowledged that “it’s a fair question” to wonder if the anti-trafficking campaign is, in part, a path to placing himself on the ballot in future years. But the answer is no, Kelly said.

“I have no plans,” he said of his political future, “and no plans to make plans.”